Fused quartz optical flat -- 6" diameter and 1" thick -- with Clausing's Diamond-Brite coating. The flat was intended for use in a project that is not going to happen now (a folded Newt), so I am selling it. The coating was done this past September, so it is essentially new, and the flat has never been used -- only taken out of its box two or three times. An added plus is both sides of the flat have been figured and are usable (but only one side is coated). $500 shipped CONUS.